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When I turn the key on the blower motor comes on at a low speed. If I turn switch to low, medium or high I get nothing. Checked fuse in the car and its good and has power. No power (pink wire) going to switch but switch tested good when I did continuity test. I next tested the blower motor relay using some info from Wilcox, If I did it correctly, it tested good and had power coming in at red wire. I read where some cars have a 30amp fuse on the red wire. I traced the wire and never found an inline fuse. Any thoughts on what to check next?
I see now you have LOW speed so you have power to the Function Control Switch. Circuit #50 (brown wire) is the feed from the fuse to the Function Control Switch.
You will see C125 (C=Connector) on the drawing.
Circuit #50 and C125 exits the main dash harness and will include the Lighter Ground eyelet and the lighter plug.
Check if you have power at C125 with ignition ON. Try unplugging it and reconnecting it, sometime it may be a bad connection.
With the Function Control Switch in ANY of the function positions except OFF you should have power on Circuit #51 (yellow wire) of the fan speed switch.
Here is a photo of the group of wires that exit the Main Dash Harness including Connector #125, Circuit 50.
Last edited by bmotojoe; Jul 13, 2022 at 10:33 PM.
Reason: Strikeout TEXT...
You will ONLY have power of the Pink Wire (early 1977) or Orange Wire (late 1977) when the Function Control Switch is in the MAX A/C setting,,,OR when Fan Speed switch is in the HI speed position.
When I turn the key on the blower motor comes on at a low speed. If I turn switch to low, medium or high I get nothing. Checked fuse in the car and its good and has power. No power (pink wire) going to switch but switch tested good when I did continuity test. I next tested the blower motor relay using some info from Wilcox, If I did it correctly, it tested good and had power coming in at red wire. I read where some cars have a 30amp fuse on the red wire. I traced the wire and never found an inline fuse. Any thoughts on what to check next?
Good to see you have the 1977 Electrical Troubleshooting Manual
These guides below are If you have NO High Speed Fan period.
If your 77 is a Early build it most likely would have the 30 amp inline fuse.
The fuse holder would be located off the TAP connector below the Brake Master Cylinder area, again early build 1977 only.
If 77 Late build,
On page 6 of the Troubleshooting Manual you will see C403 and C406 (C=Connector).
Check Connector C403 & C406. Connector C403 is prone to overheat and due to it's location prone to moister.
IF you can split 403 now would be a good time to add a dab of dielectric grease to the FM side.
The RED wire to C403 comes from the starter solenoid (Fusible link "A") then jumpers back to C406 and to Fan High Speed Relay (Red Arrows in my photo) Late build 77.
Truth is this isn't very hard to Troubleshoot. But it becomes much easier if we know if you have a early or a late 77.
Simple way to tell if your car is still original.
Do you have the alarm key switch in the drivers side front fender? Yes? You have a early build. No? (and it's not been eliminated and filled in). Then you have a late build.
As you can see. there are a number of differences between early 77 and late. I've owned both. Air-conditioning systems are VERY different. As such so is the wiring for the blower fan.
I do know I have an early 77 car. I still can’t find the inline fuse. Going to look again this weekend and try and troubleshoot a little more. Im a newby at electrical but hopefully I can figure it out.
For now forget about the 30 amp fuse.
Using the drawing you provided above you will see Circuit #50 Brown Wire, you have confirmed you have a good fuse and with ignition ON fan runs on LO because it jumpers at the Function Control Switch connector directly to the blower resistor.
Circuit #50 feeds the Function Control Switch, anytime the slider lever is in the MAX-A/C, NORM-A/C, VENT, HTR, Or DEF positions the control switch will send power to Circuit #51 Yellow Wire on the Fan Speed Switch.
If you have no power on the Yellow Wire at the fan speed switch in ANY of the positions above you have a Function Control Switch problem.
Test that first.
I will provide a photo of the Circuits of the Function Control Switch and how they relate to the Fan Speed Switch.
bmotojoe, I got it working!! Cleaned up the connections and made sure the wiring was correct. I think c403 was reversed. I now have all speeds working. Next up is getting the ac working. Thanks so much!
bmotojoe, I got it working!! Cleaned up the connections and made sure the wiring was correct. I think c403 was reversed. I now have all speeds working. Next up is getting the ac working. Thanks so much!
Good On You
Yes, early 1977 doesn't have either C403 or C406 as shown on my late 77 photo.
On the late 1977 W/AC I have a starter extension harness that includes both connectors that connects to the main engine harness.
A replacement harness is about $95.00
On your early 1977 you have a complete engine harness and a replacement is about $265.00
Get yourself a tube of dialectic grease at any local auto parts store.
When you split a connector open just give each terminal a small dab of the grease.
It is also good for light bulb sockets, spark plug wires etc.
77 Blower Switch Not Working
